Method of surface finishing cast concrete panels

ABSTRACT

This invention relates to a method of surface finishing cast concrete panels with a ribbed finish and the aggregate between the ribs exposed as to shape. The method comprises the steps of pouring a wet concrete into a casting bed in the form of a concrete panel, forming ribs in the exposed surface of said wet concrete and exposing the aggregate as to shape on the upper surface of the ribs by moving a plurality of rotating discs over the wet concrete surface. The discs are mounted in spaced relation on a shaft, and the movement of said discs at their lower extremities due to their rotation and the movement of said discs due to their movement across the surface of said wet concrete being in the same direction, said shaft and said discs driving a furrow of wet concrete in advance thereof across the surface of said concrete.

Nov. 27, 1973 T. w. STEENSON ET AL 3,775,529

METHOD OF SURFACE FINISHING CAST CONCRETE PANELS Filed Aug 23. 1971 3 Sheets-Sheet I INVENTORS. THOMAS W. STEENSON WILLIAM D. PATON Y B f ATTORNEYS Nov. 27, 1973 T. w. STEENSON ET AL 3,775,529

METHOD OF SURFACE FINlSHlNu' UAST UUNURETE 'ZANELS Filed Aug. 25 1971 5 Sheets-Sheet k AC'CEPTABLE AGGREGATE EXPOSURE SUCT/ON CLEAR SPAC/NG BETWEEN o/scs [mm/5s) FIG. 4

INVENTORS. THOMAS W. STEENSON WILLlAM D. PATON WmEEim zgif AT TORNEYS Nov. 27, 1973 T. w. STEENSON ETAL ,7?55

METHOD OI SURFACE FINISHING CAST LJIINLIIIIETI". IANIFILS Filed Aug 23, 1971 5 Sheets-Sheet 3 -AccPrAaL AGGREGATE EXPOSURE M/N. I y I 6'4 I I O 1 2 3 CLEAR SPA C/NG BETWEEN o/scs [we/15$) FIG. 7

I NVENTORS. THOMAS W. STEENSON WILLIAM D. PATON ATTORNEYS United States Patent 3,775,529 METHOD 0F SURFACE FINISIHNG CAST CONCRETE PANELS Thomas W. Steenson, 408A Mary Bay Crescent, and William Donald Paton, 190 Driscoll Road, both of Richmond Hill, Ontario, Canada Filed Aug. 23, 1971, Ser. No. 174,001 Claims priority, application Canada, Aug. 6, 1971, 119,957 Int. Cl. B281: 11/22 US. Cl. 264-162 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a method of surface finishing cast concrete panels with a ribbed finish and the aggregate between the ribs exposed as to shape. The method comprises the steps of pouring a wet concrete into a casting bed in the form of a concrete panel, forming ribs in the exposed surface of said wet concrete and exposing the aggregate as to shape on the upper surface of the ribs by moving a plurality of rotating discs over the Wet concrete surface. The discs are mounted in spaced relation on a shaft, and the movement of said discs at their lower extremities due to their rotation and the movement of said disc due to their movement across the surface of said wet concrete being in the same direction, said shaft and said discs driving a furrow of wet concrete in advance thereof across the surface of said concrete.

This invention relates to a method and a machine for architecturally finishing concrete panels with a rough ribbed finish.

For many years architecturally finished concrete panels having a rough ribbed finish for making walls and the like have been manufactured by the cast face down method where the architectural finish on the concrete panel is achieved by casting the concrete against a ribbed sculptured form, stripping the product from the form after it has set and then hand roughening the ribbed sculptured surface of the concrete to expose the aggregate and achieve the desired effect. The hand finishing operation is time consuming and costly.

This invention relates to a method and to a machine for finishing concrete panels wherein the concrete finishing operation is performed on the top surface of the wet concrete in the mould.

It is, therefore, an object of the invention to provide a method and a machine for architecturally finishing concrete that avoids the costly hand finishing operations of the prior art.

The method of surface finishing cast concrete panels with an exposed aggregate ribbed finish according to this invention comprises the steps of pouring a wet concrete mix into a casting bed; forming ribs in the exposed surface of said wet concrete and exposing aggregate as to shape on the upper surface of the ribs by moving a plurality of rotating discs over the concrete surface, said discs being mounted in spaced relation on a shaft; the movement of said discs at their lower extremities due to their rotation and the movement of said discs due to their movement across the surface of said wet concrete being in the same direction, said shaft with said discs driving a furrow of wet concrete in advance of its travel across the surface of said concrete.

The method and the machine for practising the method will be apparent after reading the following detailed specification in conjunction with the drawings.

In the drawings:

FIG. 1 is a perspective view of a concrete finishing machine according to the invention;

FIG. 2 is a view of a portion of a roller fitted with discs;

FIG. 3 is a sectional view along line 33 of FIG. 2 showing the manner in which the discs of the roller of FIG. 2 penetrate the concrete;

FIG. 4 is a graph showing the relationship between suction, rib width and surface roughness;

FIG. 5 is an alternative disc design;

FIG. 6 is a detail of a rib formation; and

FIG. 7 is a graph like FIG. 4 but for the discs of FIG. 5.

Pre-cast concrete panels are manufactured in a long line process. Continuous steel side forms 10 usually spaced apart 8 to 10 feet extend upwardly from a bottom form 12. Transverse bulk heads (not shown) extend between the side forms 10 to form the exact panel length. Additional longitudinal forms can be used to make panels of more narrow width. The forms 10 are usually adjustable vertically from 4 to 12 inches in one inch increments, depending upon the required panel thickness. Casting apparatus of this general nature is Well known and not described in detail in this application.

This invention is concerned with the architectural finish ing of the top surface of concrete 14 cast between the forms 10, and FIG. 1 shows a machine developed for this purpose.

The machine generally comprises a carriage having a steel frame, indicated by the numeral 16, with wheels 18 that ride on tracks 20 that extend longitudinally of and coeXtensively with the forms 10.

A roller generally indicated by the numeral 22 is rotatably mounted at each of its ends in a block 24 and can be raised or lowered with respect to the top surface of a body of concrete 14 in the mould by operation of the hand cranks 26. The threaded shanks of the cranks 26 are journalled adjacent each of their ends in the corners of the frame as illustrated and they threadedly engage with the roller block 24 so that as the cranks are turned, their respective roller blocks move up or down the shank of the crank, depending upon the direction of rotation.

The numeral 28 refers to an electric motor which is adapted to rotate the rollers 22 Within their blocks 24 through a gear box 30, drive belt 32 and its associated gears. Each gear box 30 has a control lever 31 for controlling the speed and direction of rotation of the rollers 22. It also has a clutch for engagement and disengagement from the power source 28.

It will be noted that there is a roller 22 at each end of the machine. The drive and construction of each roller is similar.

The machine is propelled along the tracks 20 by means of the electric motor 29 and, in this connection, drive power is transmitted through the gear box 34, belt 36, shaft 38 and belts 40 and associated gears illustrated. Motor 29 is speed and direction controlled by the manually operated electric control panel 41, whereby the speed of the carriage along the tracks can be adjusted, as will be apparent later.

The numeral 42 refers to guards intended to keep excess concrete within the moulding machine during use.

Thus, the machine for practising the invention consists essentially of a frame 16, two rotatably mounted rollers 22, which extend transversely of the frame, means for rotating the rollers, means for supporting the frame over a concrete panel casting bed with the rollers traversing the bed, means for vertically adjusting the height of the rollers 22 to control the height of the rollers with respect to the surface of concrete in the bed and means for moving the carriage frame longitudinally of the concrete bed.

The machine is especially useful for surfacing cast concrete panels with a ribbed finish wherein the aggregate of the concrete is exposed as to shape on the upper surface of the ribs. This effect is achieved by mounting discs in spaced apart relation on the rollers and rotating the discs as the machine moves along the concrete surface so that the marginal portions of the discs enter the wet concrete to form ribs and a sucking action is created on the upper surface of the ribs. The sucking action is created by rotating the discs in a direction such that the movement of the discs due to their rotation at their lower extremities and the movement of the discs due to their movement over the surface of the wet concrete is in the same direction.

Reference is made to FIGS. 2 and 3 of the drawings. FIG. 2 shows a portion of a roller 22 and two spaced apart discs 44 secured to the roller by means of set screws 46 which enter into threaded radially extending holes in the disc 48 and which bear against the roller 22. Discs similar to discs 44 are mounted all the way across the roller 22, as indicated in FIG. 1, so that as the frame of the machine is moved along the tracks 20, the marginal portions of the disc enter the concrete and form spaced apart ribs in the upper surface thereof.

The wet concrete, generally indicated by the numeral 14, has coarse aggregate, i.e. small pieces of stone, therein and it is desired to expose portions of these stones as to shape at the upper surface of the ribs. It has been found that if one rotates discs such as discs 44 in the direction indicated in FIG. 3 by the arrow 48 when the machine is moved along a bed of concrete in a direction indicated by the arrow 50, a sucking action is achieved on the upper surface of the concrete ribs that are formed by the discs. The discs as they form the ribs tend to push coarse aggregate to the upper surface of the ribs. The sucking action removes some of the cement paste at the surface which tends to expose the shape of the coarse aggregate.

The rollers tend to drive a furrow of wet concrete before them as they move along the bed, as indicated by the numeral 52. It will be appreciated that the sectional view illustrated in FIG. 2 is a section which shows the concrete directly under the lowermost part of the roller 22 and behind the furrow 52.

It will be noted that the sides of the discs 44 are tapered outwardly from the outer extremity of the discs. This is done on larger size discs to reduce the amount of suction.

An alternative design of disc is illustrated in FIG. 5. In this case, the discs do not have tapered sides. They are of a smaller dimension. They do not penetrate the concrete to as great an extent as the discs illustrated in FIG. 2. The sucking action of the rotating discs is a function of the spacing between the discs as well as the penetration of the discs into the concrete. The suction is reduced as the discs are spaced further apart.

The speed of rotation of the discs must be varied depending upon the slump of the concrete and in operation it is usual for the operator to continuously vary speed of the rotating discs with variations in slump along the length of the bed. A four inch slump concrete requires a faster disc rotation for a given carriage speed than a six inch slump. It has been found that finishing concrete with a four inch slump and discs similar to those of FIG. 2 requires a rotational speed of between 400 and 600 r.p.m., whereas a concrete having a six inch slump requires a rotational speed of between 200 and 400 r.p.m. The essential thing about the speed of the disc at any given speed of carriage is that it be fast enough to achieve the sucking action to expose the coarse aggregate. Too slow a speed of rotation will tend to drag the aggregate and tear the ribs apart. Too fast a speed will throw cement paste so that it is impractical work. Correct speed in any given situation can be readily determined by an operator.

The operator preferably sits on a platform of the carriage and adjusts the speed and height of rollers in operation to achieve the desired resul The deck Platform the frame extends over the drive assembly but has been omitted from the drawings for clarity.

The speed of operation of the carriage along the track is preferably between seven and one hundred feet per minute. Good results have been achieved at about twentyfive feet per minute.

The discs 54, illustrated in FIG. 5, have an outside diameter of 7 /2 inches and a thickness of A of an inch. The roller 22 has a diameter of 5% inches. It has been found that a good quality panel with coarse aggregate exposed on the upper surface of the ribs can be achieved by operating such a disc over the surface of wet concrete poured into a casting mould with a inch spacing between the discs. FIG. 6 illustrates a cross-section of two ribs of a panel so formed and it will be noted that the coarse aggregate 56 on the top of the ribs is exposed as to shape. This is achieved by the sucking action of the discs as they rotate in the direction of the arrow 48 and as the rollers are advanced in the direction of the arrow 50 as seen in FIG. 3.

The discs form the concrete as they pass through it along the line 58. After passage of the discs, the concrete between the ribs will tend to slump slightly to a surface shape indicated by the numeral 60.

When making ribs of narrow width such as the one illustrated in FIGS. 5 and 6, one must be careful to use a coarse aggregate ingredient small enough that it will not bind between the discs. The aggregate must also have rounded corners to avoid jamming. Generally speaking, for a inch spacing between the discs, the aggregate must be less than of an inch in its largest dimension and of rounded characteristics.

When one forms narrow ribs where jamming of the aggregate may be a problem, it is preferable to use a special facing mix. A typical facing mix having an aggregate suitable for finishing in this way is as follows:

Lbs. per cubic yard The slump of the mixture should be between four and six inches.

The amount of gravel stone in the foregoing formula can be decreased if a more sandy finish is desired. The mixture is a matter of preference and skill in the art.

The clear spacing between the discs (finished width of top surface of rib) and the penetration of the discs into the concrete is a matter of preference subject to certain practical limitations; for example, 78 of an inch clear spacing between the discs is getting towards the minimum spacing between the discs because it is not practical to use suitable aggregate that is small enough to avoid the binding problems between the discs noted above.

As well as spacing between the discs, one can vary the width of the discs. For example, one could mount two discs similar to those shown in FIG. 5 together to form a double width groove.

However, as one increases the spacing between the discs, the amount of suction is reduced. Also, as indicated above, as one increases the depth of penetration of the discs, the amount of suction is increased.

To achieve the correct amount of suction with variation of disc design and disposition on the shaft is a matter of mechanical arrangement of the discs that one can quite readily determine in any given circumstance.

The amount of suction to be achieved must be that amount that will produce the desired arrangement of the aggregate and exposure of the aggregate on the upper surface of the ribs. If the suction is too great, the coarse aggregate is torn from the upper surface of the formed ribs. If it is not enough, the upper surface is merely rippled and no stones are exposed.

FIG. 7 is a graph illustrating aggregate exposure with variations of suction and clear spacing between the forming discs or rib Width for a one inch deep rib (shallow rib) with the discs having parallel sides as illustrated in FIG. 5 and tapered sides as illustrated in FIG. 2.

The hatched area indicates the area of acceptable aggregate exposure. The line 62 is a line which shows variation of suction for a disc similar to the disc 54 and having parallel sides with variations of spacing between the discs. The spacing is indicated in inches on the graph and it will be noted that one achieves an acceptable aggregate exposure for spacing between the discs of somewhat less than one inch up to something slightly less than two inches. For spacings sub stantially less than an inch, the suction is too great and would tear the aggregate from the surface. For spacings over two inches, there is not enough suction to get a good exposure.

The line 64 shows the effect of tapering the sides of the discs and it will be noted that when the disc sides are tapered, the suction is very much reduced and that the variation in spacing between the discs for acceptable aggregate exposure is very much less.

As indicated above, however, as penetration of the discs increases the suction increases and it is sometimes necessary to reduce the suction where there are deep penetrations by tapering the discs as indicated in FIG. 2 of the drawings. 'FIG. 4 shows a graph similar to the graph of FIG. 7 but for discs that penetrate into the concrete 2 /2 inches as distinct from the 1 inch penetration of FIG. 7. In this case the numeral 66 is a line indicating suction and the disc spacing and it will be noted that if the sides of the discs are parallel, the suction is in all cases too great and tends to rip the aggregate from the surface. This is overcome by tapering the discs and when this is done the suction for rib spacings is indicated by the line 68. It will be noted that an acceptable amount of suction can be achieved with a 2 /2 inch penetration and the tapered disc with disc spacings of just under 2 /2 inches to over 4 inches. Below the hatched area of the graphs (FIGS. 4 and 7), the resulting suction causes ripples only and does not expose the shape of the stone.

The question of varying the penetration and spacing between the discs to achieve the correct amount of suction in any given case is a matter of experimentation and design. The essential thing is that the discs be rotated so that their movement at their lower extremities due to their rotation and the movement of the discs due to their movement across the surface of the wet concrete is in the same direction to achieve the sucking action on the upper surface of the ribs to expose the shape of the coarse aggregate.

As pointed out above, one does not need to be concerned about stones binding between the discs with the larger spacings between the discs. With larger spacings, one can use angular aggregate with greater assurance.

It has also been found that in the case of ribs over one inch deep, the concrete between the ribs tends to slump unduly after the sucking action has been applied and this is overcome in the case of deep rib formations in cases where it occurs by pressing the ribs to reform them by moving a second roller with discs over the grooved surface but, in this case, the discs are rotated in the opposite directions so that they do not suck on the upper surface of the ribs. On this second pass of the discs, they are rotated in the opposite direction to the arrow 48 shown in FIG. 3 for a movement of the disc 50 in the direction indicated in FIG. 3. Preferably where this pressing action is desired, rollers 22 at each end of the machine are fitted with identical discs which are aligned with each other in the direction of travel and the machine is operated over the concrete surface with the leading roller operating in the direction indicated in FIG. 3 to apply the sucking action that forms the upper surface of the concrete between the ribs to expose the aggregate and with the trailing roller operating in the opposite direction to press and reform the ribs between the upper surfaces where they have unduly slumped. The trailing roller is preferably slightly lower than the leading roller to get good contact with the ribs.

As indicated above, the exposure of the coarse aggregate is an exposure as to form only and the aggregate does tend to have a film of cement over it. If it is desired to remove this and expose the coarse aggregate as to color, it is achieved by a sand blast or acid etching operation.

From the foregoing it is apparent that the inventive concept of this invention is capable of very considerable variation. Essentially, the invention consists of the exposure of the coarse aggregate of a concrete mixture above the top surface of a rib formation by rotating a disc over the concrete surface to form the rib and apply a force to the coarse aggregate that will expose it. The force must be sufficient to expose the aggregate and it is a function of the depth of penetration and spacing between the discs. Speed of rotation of the discs is something that a person skilled in the art has little trouble arranging to get the desired result.

In order to form a panel according to this invention, one pours the wet concrete into the mold as above indicated. The carriage is then passed over the surface of the concrete with the discs engaging in the concrete in a leveling or screeding pass. The first pass of the machine is, generally speaking, a leveling one and not one adapted to form the grooves with the aggregate exposed. In the screeding operation, the discs are rotated in the same direction as they are for the suction step.

In cases where a deep rib is formed and where pressing of the ribbed formation is necessary, it will likely be necessary to pass the carriage over the concrete surface twice. On the first pass, the leading roller would be operated as a rough screeding roller. On the second pass, the leading roller would be operated as a roller to expose the aggregate on the upper surface of the ribs and the trailing roller would be operated to perform a pressing function described above.

In the specification the raising of the aggregate on the top surface of the ribs has been attributed to a sucking action. We are not certain of the theoretical explanation of the effect we achieve. We believe it to be sucking but it might equally be a lifting action applied to the coarse aggregate achieved by the shear forces applied to the concrete by the discs as they rotate in the described direction. In any event, the aggregate can be raised by rotating the discs in the same direction as the direction of travel of the carriage.

The embodiments of the invention in which an exelusive property or privilege is claimed are defined as follows:

1. A method of surface finishing cast concrete panels to provide a ribbed finish with aggregate at the surface of the ribs exposed as a shape, comprising the steps of:

pouring a wet concrete mixture having an aggregate content into a casting bed in the form of a concrete panel; forming ribs in the exposed surface of said wet concrete and raising aggregate to the upper surface of the ribs to expose the aggregate as to shape thereat by advancing a plurality of parallel spaced apart discs rotating on a shaft with their lower peripheries penetrating through the surface of the wet concrete and compressing grooves therein interspersed between adjacent ribs having uncompressed upper surfaces, and the discs rotating rapidly enough to raise aggregate upwardly between said discs to the upper surface of the ribs formed between adjacent discs;

the movement of said discs relative to the concrete at their lower extremities due to their rotation and due to their advance across the surface of said wet concrete being in the same direction; and

said discs driving a furrow of wet concrete in advance thereof across the surface of said concrete.

2. A method of surface finishing cast concrete panels as claimed in claim 1 including the additional step of pressing said grooves between the upper rib surfaces by moving a plurality of rotating discs along the grooves, the movement of said discs at their lower extremities due to their rotation and the movement of said discs due to their movement across the surface of said wet concrete being in the opposite direction.

3. A method of surface finishing concrete as claimed in claim 1 in which said exposed aggregate on the upper surface of said ribs is cleaned to expose color after said concrete has set.

4. A method of surface finishing concrete as claimed in claim 2 in which said exposed aggregate on the upper surface of said ribs is cleaned to expose color.

References Cited UNITED STATES PATENTS ROBERT F. WHITE, Primary Examiner 0 T. P. PAVELKO, Assistant Examiner US. Cl. X.R. 

